Capacity control mechanism for centrifugal gas compressors

ABSTRACT

A PAIR OF CAPACITY CONTROL DAMPER PLATES OF SEMI-CIRCULAR FORM ARE MOUNTED FOR MOVEMENT ABOUT A COMMON PIVOT IN THE GAS INTAKE PASSAGE OF A CENTRIFUGAL COMPRESSOR. THE ADJACENT STRAIGHT OR DIAMETRICAL EDGES OF THE PLATES EXTEND NORMAL TO THE AXIS OF THE PIVOT. A POWERED ACTUATOR IS MOUNTED UPSTREAM FROM THE VALVE PLATES AND IS CONNECTED TO THE SAME BY LINKS. THE PLATES ARE MOVED IN UNISON IN OPPOSITE DIRECTIONS ABOUT THE PIVOT BY THE ACTUATOR, BETWEEN POSITIONS WHEREIN THE PLATES EXTEND   TRANSVERSELY ACROSS THE PASSAGE AND A POSITION IN WHICH THE PLATES ARE PARALLEL WITH THE PASSAGE.

June 27, 1972 G. L. MOUNT 3,672,786

CAPACITY CONTROL MECHANISM FOR CENTRIFUGAL GAS COMPRESSORS Filed NOV. 2, 1970 2 ShTGtSJ-Sht 1 cu r+ 1S S2 Ll- 1 g //////////A INVENTOR.

GORDON L. MOUNT ATTORNEY G. 1.. MOUNT 3,672,786

CAPACITY CONTROL MECHANISM FOR CENTRIFUGAL GAS COMPRESSORS June 27, 1972 2 Sheets-Sheetg Filed Nov. 2, 1970 moi ' INVENTOR. GORDON L. MOUNT ATTORNEY United States Patent ee 3,672,786 Patented June 27, 1972 3,672,786 CAPACITY CONTROL MECHANISM FOR CENTRIFUGAL GAS COMPRESSORS Gordon L. Mount, West Monroe, N.Y., assignor to Carrier Corporation, Syracuse, NY. Filed Nov. 2, 1970, Ser. No. 85,937

Int. Cl. F04d 15/00, 27/00; H01j 39/12 US. Cl. 415-147 3 Claims ABSTRACT OF THE DISCLOSURE A pair of capacity control damper plates of semi-circular form are mounted for movement about a common pivot in the gas intake passage of a centrifugal compressor. The adjacent straight or diametrical edges of the plates extend normal to the axis of the pivot. A powered actuator is mounted upstream from the valve plates and is connected to the same by links. The plates are moved in unison in opposite directions about the pivot by the actuator, between positions wherein the plates extend transversely across the passage and a position in which the plates are parallel with the passage.

BACKGROUND OF THE INVENTION Many forms of inlet damper or guide vane capacity control arrangements have been devised for use in centrifugal compressors. Such arrangements have the disadvantage in that they embody a multiplicity of parts, costly to manufacture and assemble in the compressor, and expensive and sometimes difficult to maintain. The capacity control of my invention includes a nominal number of parts produced at low cost and which are convenient to assemble and service.

SUMMARY OF THE INVENTION A pair of damper plates are mounted in the compressor intake passage on a common pivot. The plates are of semi-circular form and are arranged with their straight edges extending normal to the pivot axis. Each plate is connected by a link to a prime mover which functions to simultaneously move the plates about the pivot in opposite directions from closed to open position. Due to the form and movement of the damper plates from closed position toward open position, they impart a swirl of considerable magnitude to the gas, the swirl being in the direction of rotation of the impeller, effecting a reduction in the load on the impeller driver.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a lengthwise sectional view of a portion of the intake manifold and contiguous portion of a centrifugal compressor, the view including an embodiment of my invention shown in side elevation;

FIG. 2 is a transverse sectional view taken on line 22 of FIG. 1;

FIG. 3 is a view taken on a line corresponding to line 33 of FIG. 1 with a portion of the intake manifold in section; and

FIG. 4 is a view taken on line 4-4 of FIG. 1 with the damper plates moved from closed position about 45 degrees towards open position, the view illustrating the swirl imparted to gas passing through the manifold.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, designates a portion of the casing of a centrifugal gas compressor and including an inlet portion 11. An impeller 12 is mounted on a power driven shaft 13 journaled in the casing. An intake manifold 17 is fixed to the inlet portion 11 of the compressor,

as by screws 18. As shown in FIG. 1, the manifold is formed with a downwardly curved portion 20. A pivot pin 21 is disposed diametrically across the intake passage 23 of the manifold 17. A pair of damper plates 25, 27 are pivotally mounted in side-by-side relation on the pin 21. These plates are semi-circular in form, their straight or diametrical edges being indicated at 28 (FIGS. 2, 3 and 4), and extend normal to the axis of the pivot pin 21. The ends of the pin may be journaled in bearing caps 22 threaded in the side wall of the intake manifold. That arrangement prevents the escape of gas from the manifold.

Each of the damper plates is formed with an ear or projection 31 on the side of the plate facing upstream in the passage 23. An actuator, shown as a motor 33 having a gear reduction, is mounted in an area or chamber 35 formed in the manifold 17 and offset from the intake passage 23 (see FIG. 1). The output shaft 37 of the actuator 33 is provided with a crank arm 40' having a journal 41. Links 43 are pivotally connected at like ends to each of the ears 31; and at their opposite ends, the links 43 are journaled on the crank throw 41. The chamber 35 is provided with a removable closure 45, the closure being attached to the manifold by screws 47.

In FIGS. 1 and 2, the damper plates 25, 27 are shown in closed position; that is, the plates extend diametrically across the intake passage 23, closing the same. Upon energization of the actuator 33, rotation of the crank 40, in conjunction with the links 43, effects pivotal movement of the damper blades 25, 27 about the pin 21 to the position indicated in the dotted outline, FIG. 1. In this position, the damper plates lie parallel to the passage 23, permitting full flow of gas to the impeller 12.

It is to be noted that the ears 31 on damper plates 25, 27 are located on opposite sides of the pivot pin 21 (see FIGS. 1 and 2). Accordingly, upon operation of the actuating motor 33 the bottom portion of plate 27 is moved forwardly. Simultaneously, the top portion of plate 25 is moved forwardly, that is, the damper plates 25, 27 are tilted in opposite directions.

Referring to FIG. 4, the damper plates 25, 27 have been moved from the closed position shown in solid line in FIG. 1 partially toward the open position shown in the dashed line in that figure. Upon such movement, the lower portion of the plate 27 is moved toward the impeller 12; therefore, gas moving through passage 23 sweeps downwardly along the inclined plate 27. On the other hand, the damper plate 25 is tilted in the opposite direction so that the gas sweeps upwardly along the plate 25. As disclosed, the plates 25, 27 are of semi-circular form. Accordingly, as the gas sweeps upwardly along the inclined plate 25, and contacts the curved wall of the manifold 17, circular motion is imparted to the gas, such motion being indicated by the arrows '50 in FIG. 4.

In like manner, the gas leaving the plate 27 moves in a circular path indicated by the arrows 51. There is therefore a swirling motion imparted to the gas by the plates 25, 27 as they are moved toward and from open position. The movement of the gas as viewed in FIG. 4 is in a counterclockwise direction, as viewed toward the impeller, the movement is in a clockwise direction, and the impeller is rotated in that direction.

Imparting the swirling or rotating motion to the gas in the direction of impeller rotation reduces the load on the impeller driver and accordingly elfects a reduction in power consumption. This is particularly important upon start-up of the compressor in that the impeller is not fully loaded until the damper plates have been moved about the pivot rod 21 to the full open position shown in solid line, FIG. 1.

It will be apparentthat while my invention employs a structural arrangement much less complicated than 3 variable guide vane structures now in use, such for example as the conventional annular series of journaled guide vanes, my invention nevertheless functions to impart a swirl to the gas during movement of the damper plates about the pivotal support.

I claim:

1. A centrifugal gas compressor having a gas intake passage for the flow of gas into the compressor, a split damper capacity control mechanism for controlling the flow of gas through said passage to the compressor, said split damper mechanism comprising a pivot pin extending in a direction diametrically of said intake passage, a pair of semi-circular damper plates having diametrically extending straight edges and mounted for movement about the axis of said pivot pin, the diametrically extending straight edges of said plates being disposed in close proximity and extending in a direction normal to the axis of said pivot pin, said pivot pin extending through said damper plates normal to the straight edges thereof, the ends of said pin terminating in closed cap members mounted in the wall of said intake passage, said plates in co-planar position extending transversely of said passage serving to close the same, a power-operated driver means mounted in said passage in upstream relation to said plates, a pair of links extending from said powered driver means and being pivotally connected at their like ends to said plates respectively, said driver in conjunction with said links being operable to move said plates 4 in unison in opposite directions about said pivot pin from said co-planar closing relation to a second position with said plates extending parallel to said passage for the free flow of gas through said passage.

2. A centrifugal gas compressor as set forth in claim 1, wherein said gas intake passage is formed with an offset chamber located upstream from said damper plates, and said power-operated driver means is fixedly mounted in said chamber.

3. A centrifugal gas compressor as set forth in claim 1, wherein said power-operated driver means consists of a motor unit having an output shaft, a crank member fixed to said output shaft, the opposite ends of said links being pivotally connected to said crank.

I References Cited UNITED STATES PATENTS 3,265,000 8/1966 Tyler et a1. 415-157 3,432,142 3/ 1969 Ludford 251-212 FOREIGN PATENTS 533,382 2/1941 Great Britain 415-l48 1,044,013 6/1953 France 4 15-148 HENRY F. RADUAZO, Primary Examiner US. Cl. X.R. 2512'12 

